Many of the cellular polyvinyl chloride (PVC) trim board manufacturers have used heated, rolling wheels to seal the edge of their trim boards, such as disclosed by U.S. Pat. No. 8,333,582 and published application US 2013/0099416 (both incorporated herein by reference). While such earlier process was an improvement from the un-sealed, open cell structure from the prior vintage of trim boards, the sealed edges from this process did not fully seal the surface, and did not provide an edge that was materially similar to the extruded top and bottom surface of the trim boards. The standard test to estimate how well the edge was sealed was “the pencil test”. This included drawing a line with a graphite lead pencil and then attempting to erase the line with the pencil's eraser. Any open cell structure would capture graphite in the cells which could not be removed with the eraser and indicate that the surface was not fully sealed.